JPH10274810A - Projection type image display device - Google Patents

Abstract

(57) [Problem] To provide a projection type image display device which is bright, has a high resolution and a wide color reproduction range. SOLUTION: A light source 1, a parabolic mirror 2, and a polarization beam splitter (PBS) 3 are provided, and the difference between the cut-off wavelengths of the P-polarized light and the S-polarized light reflected by the PBS 3 is 50.
%, It is incident on the cross dichroic prism 4 which is 40 nm or less. The cross dichroic prism 4 reflects the R and B wavelength ranges of the light from the PBS 3 and
After the light is separated by transmitting the light in the wavelength ranges described above, the reflective liquid crystal display elements 5-R, 5-G,
-B, and the reflected light is recombined by the cross dichroic prism 4. Then, only the light whose polarization has been rotated by the reflection type liquid crystal display element 5 to become P-polarized light passes through the PBS 3 and is projected on the screen 8 through the projection lens 7, and the S-polarized light is returned to the light source 1 side. It is.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a projection type image display apparatus which is applied to, for example, a compact projection type color liquid crystal television system or information display system and performs color display with three image display elements.

[0002]

2. Description of the Related Art A liquid crystal display device is configured to display images and characters by changing the optical characteristics of liquid crystal by applying independent drive voltages to pixel electrodes arranged regularly in a matrix. Have been. As a method of applying an independent drive voltage to the pixel electrode described above,
There are a simple matrix system and an active matrix system in which a non-linear two-terminal element or three-terminal element is provided in a liquid crystal display element.

In the latter case, a switching element such as an MIM (metal-insulator-metal) element or a TFT (thin film transistor) element and a wiring electrode for supplying a driving voltage to a pixel electrode are provided. There is a need. When strong light is incident on the switching element, the element resistance in the OFF state is reduced, and not only the charge charged when a voltage is applied is discharged, but also the liquid crystal portion existing in the region where the switching element and the wiring electrode are formed. However, since a normal driving voltage is not applied and the original display operation is not performed, there is a problem that light leaks even in a black state and the contrast ratio is reduced.

Therefore, when the liquid crystal display element is of a transmission type, as shown in FIG. 10, a TFT substrate provided with a switching element such as a TFT 101 and a pixel electrode is provided on a counter substrate opposed to the liquid crystal layer. It is necessary to provide a light-blocking means called a black matrix 102 to block light incident on the above-mentioned light incident area. Therefore, in the case of a transmissive liquid crystal display element, each of
In addition to T101, the gate bus line 103, and the source bus line 104, the light is also shielded by the black matrix 102, so that the area of the effective pixel opening in the pixel section, that is, the aperture ratio, is reduced.

Further, it is difficult to form these switching elements and wiring electrodes in a size smaller than a certain size due to restrictions on electrical performance and manufacturing techniques. Therefore,
As the definition of the liquid crystal display element increases, the aperture ratio further decreases as the pitch of the pixel electrodes decreases.

Next, a conventional projection type image display device using such a liquid crystal display device will be described.

A projection type color image display method using a liquid crystal display element includes a single-panel type using only one liquid crystal display element and a liquid crystal display element using three liquid crystal display elements according to three primary colors of red, blue and green. There is a plate type. The former single-panel type projects a liquid crystal display device having three primary color filter patterns such as a mosaic shape and a stripe shape by a projection optical system.
For example, it is disclosed in JP-A-59-230383.
The single-panel type uses only one liquid crystal display element and requires a simpler optical system than the three-panel type, and is suitable for reducing the cost and size of the projection system. Is cut off by the color filter, so that there is a problem that the illuminance is generally low.

[0008] On the other hand, the latter three-panel type converts white light from a light source into red, green, and blue (hereinafter, referred to as R, G, and B) light sources.
An optical system that divides each primary color light and a liquid crystal display element that forms an image based on the divided color light are independently provided, and each color image is optically superimposed to perform full color display. ing. In this three-panel configuration, a convergence adjustment mechanism and optical components for color separation / combination in three liquid crystal display elements are required.
Although the configuration is complicated, the light emitted from the white light source can be used effectively, and thus there is an advantage that the brightness can be increased as compared with the single-plate type.

However, when a transmission type liquid crystal display device is used in such a projection type liquid crystal display device, as described above, the aperture ratio decreases as the definition of the liquid crystal display device increases, and the It is difficult to obtain sufficient brightness even with a plate-type projection image display device. In order to solve this problem, a projection type image display device using a reflection type liquid crystal display element has been developed.

In the reflection type liquid crystal display element, as shown in FIG. 11, a reflection type pixel electrode 100 can be formed on a TFT 101 as a switching element. The aperture ratio can be made larger than that of the display element, which is very effective for improving the brightness in the projection type liquid crystal display device.

A polarizing beam splitter (hereinafter referred to as PBS) for separating white light from a light source into P-polarized light and S-polarized light, and white light from R, G,
A system combining a cross dichroic prism for separating into three primary colors of B has been proposed (JP-A-4-33).
8721). However, Japanese Patent Application Laid-Open No. Hei 4-338721 does not mention anything about the wavelength shift of the spectral characteristics with respect to the P-polarized light and the S-polarized light incident on the cross dichroic prism and the effect of this wavelength shift on the display characteristics of the projection. It has not been.

Japanese Patent Application Laid-Open No. 4-319910 discloses a system using a light scattering type liquid crystal display device as a reflection type liquid crystal display device and having a schlieren optical system. There is no mention of the effect of using a display element on the color separation characteristics of a cross dichroic prism.

[0013]

By the way, in the configuration of Japanese Patent Laid-Open No. 4-338721 proposed above, since the birefringent mode reflection type liquid crystal display element is used, the polarization state of light incident on the cross dichroic prism is changed. , Its outbound,
Turn 90 ° in the return path. Since the cross dichroic prism generally has a large polarization dependence on the reflection surface, the spectral characteristics are largely shifted between the case where white light is separated into R, G, and B lights and the case where white light is combined in reverse.

FIG. 12A shows an example of spectral characteristics of the B reflected light with respect to the S-polarized light and the P-polarized light of the cross dichroic prism, and FIG. 12B shows the S-polarized light and the P light of the R reflected light of the cross dichroic prism. 4 shows an example of spectral characteristics for polarized light. As can be understood from FIG. 12, both the S-polarized light and the P-polarized light enter the cross dichroic prism, but the R and B colors largely depend on the brightness and color reproduction range of the projection. P-polarized light has a narrower band than S-polarized light, and S-polarized light has a narrower band than P-polarized light for G color light.

However, if the wavelength dependence of the P-polarized light and the S-polarized light is large, as shown in FIG. 13 (a), if the brightness and the color reproduction range of the R and B color lights restricted by the P-polarized light are adjusted, The bandwidth of the G color light indicated by oblique lines is narrowed, which hinders display of the G color light and white balance. Conversely, when the brightness and color reproduction range of the G color light are adjusted, as shown in FIG.
The same problem as the above-described G color light occurs for each color light.

Further, when there is a wavelength shift of the spectral characteristics with respect to P-polarized light and S-polarized light, the following problem occurs.
As shown in FIG. 14, for example, when S-polarized light is incident on the cross dichroic prism, the reflection type liquid crystal display element 5-R corresponding to the R color light has an R band of R reflected by the cross dichroic prism 4. Polarized light (a) is incident. Then, the reflection type liquid crystal display element 5-R modulates the polarization state in accordance with the image signal and reflects the light. Therefore,
Since the modulated light contains a P-polarized light component, light (b) in a hatched portion shown in FIG. 3 described later transmits through the R reflection surface of the cross dichroic prism and corresponds to the liquid crystal display corresponding to the B color light. The light will be incident on the element 5-B. When this light is changed to S-polarized light again by the liquid crystal display element 5-B, the reflected light (c) does not return to the liquid crystal display element 5-R corresponding to the R color light, but corresponds to the G color light. The light is reflected in the direction of the liquid crystal display element 5-G. When this light is changed to P-polarized light again by the liquid crystal display element 5-G corresponding to the G color light, G
The light (d) reflected by the liquid crystal display element 5-G corresponding to the color light passes through the R reflection surface of the cross dichroic prism 4 and enters the projection lens, and is projected on the screen as stray light or ghost. Is done.

The above-mentioned problem of stray light and ghost similarly appears for light in the band B. Even when P-polarized light is incident on the cross dichroic prism 4, the problem of stray light and ghost occurs on the same principle. .

In Japanese Patent Application Laid-Open No. 4-319910, since a light scattering type liquid crystal display device is used, random polarized light basically enters the cross dichroic prism. In this case, the shift of the spectrum in the forward path and the return path does not occur. However, since the averaged spectrum of the P-polarized light and the S-polarized light with respect to the color separation surface of the cross dichroic prism is obtained, as shown in FIG. The characteristic shows a step-like characteristic when the rate is around 50%. Therefore, the color purity and light use efficiency of R, G, and B are extremely reduced.

The present invention has been made to solve such problems of the prior art, and has as its object to provide a bright, high-resolution, projection-type image display device having a wide color reproduction range.

[0020]

According to a first aspect of the present invention, there is provided a projection type image display device, in which polarized light is made incident on a color separation / combination means comprising a dichroic prism or a plurality of dichroic mirrors to separate light of a plurality of colors. After that, each color light is made incident on another reflection type image display element, and the reflection light from each reflection type image display element is made incident on the color separation / combination means to combine each color light, and projected by the projection means. In a projection type image display device for projecting, the color separation / combination means determines a difference between a cutoff wavelength for a P-polarized light component and a cutoff wavelength for an S-polarized light component, and the cutoff wavelength has a transmittance of 50%. Since the wavelength is defined to be 40 nm or less when defined as a wavelength, the above object is achieved.

According to a second aspect of the present invention, there is provided a projection type image display device, wherein a light source and light from the light source are separated into two orthogonal linearly polarized lights, and one of the two orthogonal linearly polarized lights is provided. A polarization splitting unit for causing the polarized light to be incident on the color separation / synthesizing unit, and wherein the reflection type image display element changes the polarization state of linearly polarized light from the polarization splitting unit. It is characterized by consisting of

According to a third aspect of the present invention, there is provided a projection type image display device, wherein light is made incident on a color separation / combination means comprising a dichroic prism or a plurality of dichroic mirrors to separate the light into a plurality of colors. A projection type in which each is incident on a reflection type image display element which does not depend on each polarization, and reflected light from each reflection type image display element is made incident on the color separation / combination means to combine each color light, and is projected by the projection means. In the image display device, the color separation / combination means defines a difference between a cutoff wavelength for a P-polarized component and a cutoff wavelength for an S-polarized component as the wavelength at which the transmittance becomes 50%. Since the thickness is sometimes 40 nm or less, the above-mentioned object is achieved.

In a projection type image display device according to a fourth aspect of the present invention, each of the image display elements is a light scattering type liquid crystal display element, and light scattered by the scattering type liquid crystal display element is selectively removed. A schlieren optical system is provided.

According to a fifth aspect of the present invention, in the projection type image display apparatus, each of the image display elements can change the angle of light emitted from the image display element in a predetermined direction. And an optical system that selectively removes light reflected by the reflection-type image display element according to an emission angle.

According to a sixth aspect of the present invention, there is provided a projection type image display device comprising a light source, and a light source which is reflected or transmitted by the color separation / combination means on an optical path between the light source and the reflection type image display element. A color limiting means for limiting at least one of red, green and blue wavelength bands for polarized light is provided.

A projection type image display apparatus according to a seventh aspect of the present invention includes a light source, is provided on an optical path between the light source and the image display element, and is reflected or transmitted by the color separation / combination means. It is characterized in that it comprises a color limiting means for limiting at least one of each of the red, green and blue wavelength bands for random polarization.

Hereinafter, the operation of the present invention will be described.

According to the first aspect of the present invention, since the difference between the cutoff wavelengths of the P-polarized light and the S-polarized light in the color separation / combination means is 40 nm or less, necessary light can be efficiently separated / combined. Thus, an image having a good white balance can be realized.

Here, the reason why the difference between the cutoff wavelengths of the P-polarized light and the S-polarized light in the color separation / combination means is set to 40 nm or less will be described with reference to FIG.

As shown in this figure, the wavelength at which the transmittance of the B color light and the R color light becomes 50% is 500 nm and 600 nm.
If the difference between the cutoff wavelengths is 40 nm, all of the R, G, and B color lights can be effectively used. The wavelength bands of the R, G, and B color lights are generally R: 600 to 700 nm and G: 500 to
600 nm, B: 400 to 500 nm. In this figure, the S-polarized light of the B color light and the S-polarized light of the R color light intersect at about 550 nm. That is, assuming that the rise is 20 nm, the S polarization of the B color light is 5
00 nm + 10 nm (half of rising) +40 nm
(Difference in cutoff wavelength) = 550 nm, while R
600 nm-10 nm (half of the rise)-40 nm (difference in cut-off wavelength) =
This is because it becomes 550 nm.

However, if the difference between the cutoff wavelengths is 40 nm, the light quantity of G can sufficiently secure a practical level, but the light quantity is slightly smaller than that of the R and B color lights, and the white balance can be adjusted slightly. Ideally, the difference between the cutoff wavelengths is preferably 30 nm or less.

The cutoff wavelength is defined as a wavelength at which the transmittance (or reflectance) of the color separation / combination means becomes 50%.

According to the second aspect of the present invention, by using a birefringent mode liquid crystal display element, the color purity of the projection system can be adjusted as described above for P and R polarized light incident on the color separation / combination means for R and B as described above. G is almost determined by the spectral characteristics of S-polarized light, so that the rising (or falling) characteristics at the cutoff wavelength of light shown in FIG. 16 become steep, and a bright image having a wide color reproduction range can be realized.

According to the third aspect of the present invention, by using the non-polarization mode image display element, not only the P-polarized light and the S-polarized light contained in the light from the light source can be efficiently used, but also FIG. 1 described in the case of the configuration according to item 1
For the same reason as in No. 6, a brighter image can be realized.

According to the fourth aspect of the present invention, scattered light and non-scattered light can be efficiently separated by using the reflective liquid crystal display device in the light scattering mode and the schlieren optical system, and the brightness and the contrast can be improved. High image quality can be realized.

According to the fifth aspect of the present invention, the reflection type image display element capable of changing the angle of the light emitted from the image display element in a predetermined direction, and the light emitted from the image display element can be changed according to the emission angle. By using an optical system for selective removal, a bright and high-contrast image can be realized.

According to the sixth aspect of the present invention, stray light and ghost due to a hatched portion (b) in FIG. 3 described later can be prevented by installing a color limiting means, for example, a filter.

However, when a non-polarization mode reflective pixel display element is used, random polarized light enters the color separation / combination means. Therefore, as shown in FIG. 17, the spectral characteristics of the light separated by the color separation / combination means are the average values of the P-polarized light and the S-polarized light. Is worse than when an image display element of a birefringence mode is used, and the color purity of R, G, and B is reduced. To resolve this, the following configuration of claim 7 may be adopted.

According to the seventh aspect of the present invention, by providing a color limiting means, for example, a filter, R, R due to deterioration of the rising or falling characteristic at the cutoff wavelength is reduced.
A decrease in the color purity of G and B can be prevented, and an image with a wide color reproduction range can be realized.

[0040]

Embodiments of the present invention will be described below.

(Embodiment 1) FIG. 1 is a schematic view of a projection type color image display apparatus according to this embodiment.

In this embodiment, as the light source 1, 150
W, a metal halide lamp having an arc length of 3 mm was used.
As the light source 1, a halogen lamp or a xenon lamp can be used. On the back of the light source 1, a parabolic mirror 2 for emitting light from the light source 1 as substantially parallel light is arranged.

In front of the light source 1, a PBS 3 for separating light from the parabolic mirror 2 into P-polarized light and S-polarized light is arranged.
The S-polarized light reflected at S3 enters the cross dichroic prism 4. The cross dichroic prism 4 separates the light from the PBS 3 by reflecting the R and B wavelength ranges and transmitting the G wavelength range, and then separates the reflection type liquid crystal display elements 5-R and 5 corresponding to the respective colors. -G, 5-B
Incident on

The reflection type liquid crystal display elements 5-R, 5-G, 5-
B is a 1.3-type S-VGA (pixel pitch is 33 μm).
m × 33 μm), and a display mode using a birefringent type that displays an image using polarized light was used. Therefore, the incident light is reflected by three reflective liquid crystal display elements 5-R, 5-G, and 5-B.
As a result, the polarization state is modulated according to the image signal and reflected. In the present embodiment, the exit surface 4R of R of the cross dichroic prism 4 and the reflective liquid crystal display element 5
-R, a dichroic filter 6-R is arranged between the first and second cross-dichroic prisms 4,
A dichroic filter 6-B was arranged between the reflection type liquid crystal display element 5-B. Note that G is also provided between the cross dichroic prism 4 and the reflective liquid crystal display element 5-G.
A dichroic filter may be provided. Also,
The dichroic filter may be provided so as to limit at least one of the R, G, and B wavelength bands. The position of the dichroic filter is not limited to the position between the cross dichroic prism 4 and each reflective liquid crystal display device, but may be any position between the light source and the reflective liquid crystal display device.

The light reflected by the liquid crystal display elements 5-R, 5-G, 5-B is recombined by the cross dichroic prism 4. Then, the reflection type liquid crystal display element 5-R,
Only the light whose polarization has been rotated by 5-G and 5-B to become P-polarized light passes through the PBS 3 and is projected on the screen 8 through the projection lens 7, and the S-polarized light is returned to the light source 1 side .

In the projection type color image display apparatus of the present embodiment having the above-described configuration, the light incident on the cross dichroic prism 4 is separated into R, G, and B color lights in accordance with the spectral characteristics of S-polarized light. , Reflection type liquid crystal display elements 5-R, 5-G, 5-
At B, the light is rotated to P-polarized light in accordance with the image signal, and is synthesized again by the cross dichroic prism 4. At this time,
FIG. 12A for the B color light and FIG. 1 for the R color light
As shown in FIG. 2B, both the B color light and the R color light have narrower bands in the spectral characteristics of the cross dichroic prism 4 with respect to the P-polarized light than with the S-polarized light. For this reason, the brightness and color purity are regulated by the P-polarized light, and FIG.
As shown in (1), the color light of G is constrained by S-polarized light because it has a narrower spectral characteristic with respect to S-polarized light, contrary to the color light of R and B.

Therefore, as shown in FIG.
In a cross dichroic prism having a large difference in the wavelength characteristic of the spectral characteristic with respect to the polarized light, the band of the G color light is narrowed when the R color light and the B color light are optimally designed as shown in FIG. Further, as shown in FIG. 13B, when the optimal design is performed for the G color light, the R color light,
Since the band of the B color light is narrow, it is difficult to efficiently separate the R, G, and B color lights.

The cross dichroic prism 4 applied to the present invention is designed so that the wavelength shift amount of the spectral characteristic with respect to the P-polarized light and the S-polarized light is 25 nm. For the band in S-polarized light,
As shown in FIG. 3, sufficient brightness and color purity can be obtained.

The dichroic filters 6 -R and 6 -B disposed on the R and B optical paths have the same spectral characteristics as the P-polarized light of the cross dichroic prism 4.

FIG. 2A shows the spectral characteristics of the dichroic filter 6-B corresponding to the B color light.
(B) shows the spectral characteristics of the dichroic filter 6-R corresponding to the R color light. As a function of the dichroic filters 6-R and 6-B, as described above, in order to prevent stray light and ghost due to the light in the hatched portion shown in FIG. It is for cutting off the light. Therefore, the light reflected by this filter has the same polarization direction as that at the time of incidence, and is reflected by the cross dichroic prism 4 and the PBS 3 and returned to the light source 1.

When the projection was configured under the above conditions, white light from the light source 1 could be used efficiently, and a bright image with a wide color reproduction range could be realized.

In the present embodiment, S-polarized light is made incident on the cross dichroic prism 4, but a cross dichroic prism of the same design can be used even when P-polarized light is made incident. However, in this case, since the P-polarized light having a narrower band than the spectral characteristics of the S-polarized light enters the reflective liquid crystal display elements 5-R and 5-B corresponding to the R and B color lights, respectively, Although a stray light and a ghost hardly occur to the element, a reflective liquid crystal display element 5 corresponding to the G color light is used.
−G is incident on P-polarized light having a wide band, and a part of the light is reflected as S-polarized light in accordance with the image signal. However, since the transmission band of the cross dichroic prism is narrow for S-polarized light, FIG. The hatched light shown is reflected in the direction of the liquid crystal display element corresponding to each of the R and B color lights. Therefore, since these lights cause stray light and ghost, S
Install a reflection or absorption type filter that has the same or narrower spectral characteristics as polarized light, or R, B
It is desirable to install an absorption type filter corresponding to each color light in the optical path.

The installation location and spectral characteristics of the filter described above are merely examples, and are not limited to the above embodiment.

(Embodiment 2) FIG. 4 is a schematic view of a projection type color image display device according to a second embodiment of the present invention. In the present embodiment, the same numbers are given to the same optical components as in the first embodiment.

In this embodiment, the light source 1 is installed at the first focal point of the elliptical reflecting mirror 9. Light from the light source 1 is reflected by a reflecting mirror 10 installed near the second focal point of the elliptical reflecting mirror 9 and is incident on the cross dichroic prism 4 through a condenser lens 11. The cross dichroic prism 4 separates the light by reflecting the R and B wavelength ranges of the incident light and transmitting the G wavelength range, and thereafter reflects the liquid crystal display elements 5-R and 5-R corresponding to the respective colors. G, 5-B.

The reflection type liquid crystal display elements 5-R, 5-G, 5-
As B, as shown in FIG. 5, a polymer-dispersed liquid crystal display element which contains a nematic liquid crystal in a capsule form in a polymer and displays an image by scattering light is used. In the case of the polymer-dispersed liquid crystal, when no voltage is applied, FIG.
As shown in (a), since the molecules of the liquid crystal are almost randomly oriented, scattering occurs at the interface with the polymer. On the other hand, when a voltage is applied, the liquid crystal molecules are aligned in the direction of the electric field as shown in FIG. 5B, so that the refractive index of the liquid crystal in the direction of the electric field at this time matches the refractive index of the polymer. When set, light scattering does not occur and the film becomes transparent. Therefore, the incident light is scattered and reflected by the three reflective liquid crystal display elements 5-R, 5-G, and 5-B in accordance with the image signal.

A dichroic filter 6 -R is arranged between the exit surface of the cross dichroic prism 4 for emitting the R color light and the reflective liquid crystal display element 5 -R, and the cross dichroic prism 4 emits the G color light. A dichroic filter 6 -G is arranged between the surface and the reflective liquid crystal display element 5 -G, and the B
A dichroic filter 6-B was arranged between the emission surface of the colored light and the reflective liquid crystal display element 5-B.

The reflection type liquid crystal display elements 5-R, 5-G, 5-
The light reflected by B is combined again by the cross dichroic prism 4 as shown in FIG.
At 1, the light is focused on the pupil of the projection lens 7. An aperture 12 that cuts light scattered by the reflection type liquid crystal display elements 5-R, 5-G, and 5-B and transmits non-scattered light is installed on the pupil of the projection lens 7. Only the passed light is projected on the screen 8 through the projection lens 6.

In the thus constructed projection type color image display apparatus of this embodiment, since randomly polarized light is incident on the cross dichroic prism 4, its spectral characteristic is, as shown in FIG. The average value of the spectral characteristics for the S-polarized light is obtained. Therefore, in a normal cross dichroic prism, the steepness of the rising or falling characteristics of the spectral characteristics at the boundary between the colors is deteriorated, and R, G,
The color purity of B greatly decreases. However, in this embodiment, since the same one as used in the first embodiment is used, P
The difference in the wavelength dependency between the polarized light and the S-polarized light is small, as shown in FIG. 17, and it is possible to prevent a decrease in the color purity of R, G, and B.

The dichroic filters 6-R and 6-B arranged on the R and B optical paths are shown in FIGS. 6 (a) and 6 (b).
As shown in FIG. 6, the dichroic filter 6-G having the same spectral characteristics as the P-polarized light of the cross dichroic prism 4 and installed on the G optical path has the same spectral characteristics as the S-polarized light, as shown in FIG. Since it has spectral characteristics and has a band narrower than the spectral characteristics of the cross dichroic prism 4, the color purity of R, G, and B projected on the screen 8 is substantially determined by these filters.

As described in the first embodiment, the cross dichroic prism 4 used in the present embodiment
Is optimally designed for P-polarized light for each color light and for S-polarized light for G color light, so that the color purity can be further improved as compared with the case where only the cross dichroic prism 4 is used. .

When the projection was configured under the above conditions, the use of the light-scattering type liquid crystal display device enabled efficient use of both the P-polarized light and the S-polarized light components contained in the white light from the light source. Thus, an image having a wide color reproduction range could be realized.

In the present embodiment, the filters for correcting color purity are installed on all the optical paths of R, G, and B. However, the filters need not always be installed on the optical paths that do not need to correct color purity. Instead, for example, it may be provided so as to limit at least one of the R, G, and B wavelength bands.

In this embodiment, a light-scattering type image display device is used as a non-polarization mode image display device.
"International ELECTRON D
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N, DC DECEMBER 5-8, 1993 ".
device) may be used. In this DMD element, as shown in FIG. 7, the angle of a mirror constituting each pixel can be inclined by static electricity, and the angle of light emission by the mirror is changed.

In the first and second embodiments, a cross dichroic prism in which four prisms are bonded is used as the color separating / combining means, but the present invention is not limited to this. For example, as shown in FIG.
1, 42, and 43, and FIG.
The present invention can be applied to any device capable of performing color separation and synthesis, such as a device using a plurality of dielectric mirrors as shown in FIG. FIG. 9A shows a configuration corresponding to the above-described projection-type image display device of the first embodiment, and FIG. 9B shows a configuration corresponding to the above-described projection-type image display device of the second embodiment. It is a structure of. FIG. 9 (a),
In (b), the same parts as those in FIGS. 1 and 4 are denoted by the same reference numerals.

[0066]

As described above, according to the present invention, a dichroic prism or a dichroic mirror-based color separation / synthesis means having a small polarization-dependent difference in cutoff wavelength between P-polarized light and S-polarized light of 40 nm or less is used. Bright, high-resolution images with a wide color reproduction range and excellent white balance can be realized. In addition, by providing a color limiting unit that limits the spectrum of light incident on the image display element corresponding to R, G, and B, not only stray light and ghost generated due to polarization dependence of the color separation / combination unit can be prevented,
The color purity can be further improved as compared with the case where only the dichroic prism or the dichroic mirror system is used.

[Brief description of the drawings]

FIG. 1 is a schematic diagram illustrating a configuration of a projection type color image display device according to a first embodiment of the present invention.

FIG. 2 is a diagram illustrating spectral characteristics of a dichroic filter provided in the projection color image display device according to the first embodiment of the present invention.

FIG. 3 is a diagram illustrating spectral characteristics of a cross dichroic prism provided in the projection color image display device according to the first embodiment of the present invention.

FIG. 4 is a schematic diagram illustrating a configuration of a projection type color image display device according to a second embodiment of the present invention.

FIG. 5 is a diagram for explaining a liquid crystal display element provided in the projection type color image display device according to the second embodiment of the present invention.

FIG. 6 is a diagram illustrating spectral characteristics of a dichroic filter provided in a projection type color image display device according to a second embodiment of the present invention.

FIG. 7 shows another liquid crystal display element (DM) that can be used in the projection type color image display device according to the second embodiment of the present invention.
It is a perspective view which shows D).

FIG. 8 is a diagram showing another example of a color separation / combination unit that can be used in the present invention.

FIG. 9 is a diagram showing a color separation / synthesis unit having still another configuration usable in the present invention.

FIG. 10 is an explanatory view (perspective view) of a pixel structure of a transmission type liquid crystal display element.

FIG. 11 is a sectional view of a reflective liquid crystal display device.

FIG. 12 shows spectral characteristics of a conventional cross dichroic prism.

FIG. 13 is an explanatory diagram of a problem that occurs in a conventional cross dichroic prism.

FIG. 14 is an explanatory diagram of a generation mechanism of stray light and ghost.

FIG. 15 shows spectral characteristics of a conventional cross dichroic prism with respect to random polarization.

FIG. 16 is a diagram used to explain the principle of the present invention, and is a diagram showing characteristics of a color separation / combination unit used in the present invention.

FIG. 17 shows spectral characteristics of the cross dichroic prism to which the present invention is applied, with respect to random polarized light.

[Explanation of symbols]

 Reference Signs List 1 light source 2 parabolic mirror 3 PBS (polarizing beam splitter) 4 cross dichroic prism 5-R, 5-G, 5-B reflective liquid crystal display element 6-R, 6-G, 6-B dichroic filter 7 projection lens 8 Screen 9 Elliptical Reflector 10 Reflector 11 Condenser Lens 12 Aperture

Claims (7)

[Claims] 1. A polarized light is made incident on a color separating / combining means comprising a dichroic prism or a plurality of dichroic mirrors to be separated into light of a plurality of colors, and thereafter, each color light is made incident on another reflection type image display element. A projection type image display device for causing the reflected light from each reflection type image display element to enter the color separation / combination means, to combine the respective color lights, and to project the light by the projection means. A projection type image display apparatus wherein the difference between the cutoff wavelength for the P-polarized component and the cutoff wavelength for the S-polarized component is 40 nm or less when the cutoff wavelength is defined as a wavelength at which the transmittance becomes 50%. . 2. A light source, and separates light from the light source into two orthogonal linearly polarized lights, and inputs the polarized light, which is one of the two orthogonal linearly polarized lights, to the color separation / combination means. 2. A projection-type image according to claim 1, further comprising a polarization splitting means for changing the polarization state of the linearly polarized light from the polarization splitting means. Display device. 3. A reflection-type image display device in which light is made incident on a color separation / combination means comprising a dichroic prism or a plurality of dichroic mirrors to be separated into light of a plurality of colors. And the reflected light from each reflection type image display element is made incident on the color separation / combination means to combine each color light, and projected by the projection means, wherein the color separation / combination means Is a projection image in which the difference between the cutoff wavelength for the P-polarized component and the cutoff wavelength for the S-polarized component is 40 nm or less when the cutoff wavelength is defined as a wavelength at which the transmittance becomes 50%. Display device. 4. The image display device according to claim 3, wherein each of the image display devices is a light scattering type liquid crystal display device, and further includes a schlieren optical system for selectively removing light scattered by the scattering type liquid crystal display device. Projection image display device. 5. Each of the image display elements is a reflection type image display element capable of changing the angle of light emitted from the image display element in a predetermined direction, and is reflected by the reflection type image display element. 4. The projection type image display device according to claim 3, further comprising an optical system for selectively removing the emitted light according to an emission angle. 6. A light source, and on a light path between the light source and the reflection type image display device, a red, green, and blue wavelength band for S-polarized light reflected or transmitted by the color separation / combination means. 3. The projection-type image display device according to claim 1, further comprising a color restricting unit that restricts at least one. 7. A light source comprising: a light source, a red light for random polarized light reflected or transmitted by the color separation / combination means, which is provided on an optical path between the light source and the image display element;
The projection-type image display device according to claim 4, further comprising a color limiting unit that limits at least one of each of the green and blue wavelength bands.